There are some ways of repair rtf, as only my opinion and some other familiar MS Specialists. It is the guide in the following or resources that suggest Microsoft Company
https://support.microsoft.com/en-us/help/316951/how-to-recover-a-lost-word-document
http://www.rtf.repair/
You could try Open Office Writer program. In the wiki it said that it's recovered corrupted Word documents that MS Word couldn't recover. It's a long shot, and I doubt it'll work, but it's free to try.
Try inserting the .RTF into a new Word document. To do this open Word and click INSERT -->FILE and point to the RTF file. Also try opening in Notepad by right clicking the file and selecting "Open With" and select Notepad from the list of programs.